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Friday, April 6, 2018

Fancy charging up your electric car in 10 minutes?

Fancy charging up your electric car in 10 minutes?

By Matthew Wall

Imagine being able to charge your electric car in minutes rather than hours, or your smartphone in seconds.

That's
the enticing prospect being touted by Researchers who reckon they've
discovered a new material that could boost the performance of a
carbon-based supercapacitor - sometimes called an ultracapacitor - a
type of energy storage device that can be charged very quickly and
offload its power very quickly, too.Dr Donald Highgate, director
of research at Superdielectrics Ltd, says a material he originally
developed for soft contact lenses is also surprisingly good at holding
an electrostatic field.Very
simply, supercapacitors don't produce electricity through chemical
reactions as conventional batteries do, they create these electrostatic
fields.Dr Highgate is working with Bristol and Surrey
universities to develop supercapacitors using the new polymer and hopes
that they could eventually rival, or even surpass, lithium-ion (li-ion)
batteries - so long as they manage to replicate prototype performance on
a large scale.So far, supercapacitors have been good at
providing quick bursts of power - to start a car engine, for example, or
to give trains a boost when accelerating. They're also well-suited to
harvesting energy from vehicles when they brake, making them an
important component in electric vehicles.

And national electricity grids use them to provide quick power top-ups when balancing supply and demand.South
Korea's capital Seoul is hoping to have 3,500 supercapacitor-powered
buses operating by 2020, and they're also being used in Shanghai, China.
European car maker PSA Peugeot Citroen has been using them in its cars
since 2010 - supercapacitor maker Maxwell Technologies says more than a
million vehicles now incorporate its products.But to date, supercapacitors haven't been very good at holding much power or holding on to that power for very long.This
poor energy density, as it's called, the amount of power they can hold
per kilogramme, has put them at a significant disadvantage to li-ion
batteries."The two main advantages of conventional supercapacitors over
batteries are their ability to handle much higher charge and discharge
rates, and their longer cycle life," says Gareth Hinds, Fellow of the
UK's National Physical Laboratory. "The downside is that they
tend to be relatively high cost and can only store a few seconds-, or at
most, minutes-worth of power."This isn't a problem when your
supercapacitor is being used to power a tool on a factory assembly line,
for example. It can be recharged in seconds once it's placed back in
its charging dock. But it is if you're in an electric car or bus that needs recharging every few miles.

Taavi Madiberk, chief executive and co-founder of
Skeleton Technologies, a supercapacitor maker based in Estonia, Germany
and Finland, says his products incorporate layers of graphene - a single
layer of carbon atoms arranged in a hexagonal lattice - and other
carbon-based materials in its supercapacitors.These layers have a
huge surface area - just 1g of graphene can cover 2,000 sq m, says Mr
Madiberk. This allows them to hold on to a lot more power.His
firm's products are already used in hybrid vehicles, particularly buses
and lorries. In one experiment, they installed supercapacitors in a
Sainsbury's supermarket diesel-electric delivery van and "achieved 32%
fuel savings", says Mr Madiberk.But he acknowledges that in the
short-term, combining supercapacitors with li-ion batteries is probably
the best way to enjoy the best of both worlds, particularly in electric
vehicles.

Ulrik Grape, chief executive of NaWa technologies,
another supercapacitor maker based in the South of France, agrees,
saying: "Supercapacitors don't store as much energy but their response
is instantaneous. So a supercapacitor could handle acceleration and
energy recovery under braking - taking care of the stressful part of a
battery's life - possibly doubling or tripling a battery's life
expectancy."NaWa's technology involves electrodes made from
"vertically aligned carbon and graphene nanotubes that can store the
energy on the surface of these tubes," explains Mr Grape. These
tubes, which are coated with another carbon-based material, are so tiny
you can fit 10 billion of them in a square centimetre.As carbon
is a light material, incorporating supercapacitors into li-ion batteries
would also reduce the overall weight, and this would improve the range
performance of an electric vehicle.A Formula E racing car's
battery, currently made by Williams Advanced Engineering, weighs 300kg,
but this could be reduced by a third to 200kg, NaWa believes, without
any loss of range.

"We think the ability to charge and discharge a
battery fast will be one of the most important things in the future,"
says Mr Grape."We don't have as much energy as a lithium-ion
battery but we can do many more cycles - charges and discharges - up to a
million. Carbon is such a robust material."By contrast, a normal
battery, which relies on chemical reactions to create electricity,
eventually wears out once those chemicals lose their potency - after
about 3,000 to 5,000 cycles of charging and discharging.Another advantage of supercapacitors, makers say, is that they don't require rare materials, such as cobalt.Of
course, supercapacitors don't mean the end of traditional batteries by
any means. Li-ion technology is still being improved by about 5-10% each
year.New forms of energy storage will be critical to the success
of renewable energy as a replacement for fossil fuels. When the sun
doesn't shine or the wind doesn't blow, we'll need to access stored
energy very quickly to plug the gap.As well as traditional energy
storage methods, such as pumped hydro, flywheels, compressed gas and
large battery arrays, highly efficient supercapacitors could eventually
become a crucial component in a fully sustainable energy network.But these are early days."Polymer-based
supercapacitors are emerging as a promising technology," concludes
Gareth Hinds, "but there is a lot of work still to do to achieve the
required energy storage capacity without compromising on power, lifetime
and cost."

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